This invention relates to test and measurement instruments and, more particularly, to test and measurement instruments capable of measuring parameters of digitized waveforms.
Modern digital oscilloscopes generally provide a measurement feature whereby specific waveform parameters, such as peak-to-peak voltage, rise time, pulse width, etc. are calculated for the acquired waveform data and presented to the user. A central processing unit (CPU) within the oscilloscope generally computes these measurements.
The process begins by moving a digitized waveform from acquisition memory to CPU memory where it can be processed. The first step in a measurement calculation is the generation of a vertical histogram of the digitized levels found within the waveform. This histogram is used to find key values within the waveform (high, mid, mean, etc.) These values are, in turn, used to derive the vertical measurements. Additionally, these values are used to allow the extraction of the crossing information necessary for the calculation of timing measurements.
Unfortunately, this approach to the generation of measurements requires moving the entire waveform record to the CPU memory space. Furthermore, the CPU is typically designed for general-purpose computing, not for the specific purpose of manipulating waveform data to generate a histogram. As a result, the overall waveform throughput rate, a key feature of a modern digital oscilloscope, is reduced. In order to keep the waveform throughput high, most oscilloscopes update their measurements infrequently. Consequently, the digital oscilloscope is unable to efficiently perform further functions using the measurements, such as a statistical analysis of the measurements.
Accordingly, there remains a need for a test and measurement instrument having an improved measurement speed.